Journal articles on the topic 'Commercial shark fishing'
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1
Berrow, S. D. "Incidental capture of elasmobranchs in the bottom-set gill-net fishery off the south coast of Ireland." Journal of the Marine Biological Association of the United Kingdom 74, no. 4 (November 1994): 837–47. http://dx.doi.org/10.1017/s0025315400090081.
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The incidental capture of sharks in the bottom-set gill-net fishery off the south coast of Ireland was quantified by placing observers on commercial gill-netters for the duration of a fishing trip. Forty fishing trips were sampled resulting in 1,167 km and 19,760 km h of observed fishing effort. Sixty individual sharks of seven species were reported entangled in the fishing gear. Tope, porbeagle and six-gilled sharks were the most frequently caught species, with black-mouthed dogfish, blue shark, basking shark and starry smooth hound also recorded. Total fishing effort along the south coast was calculated and total capture extrapolated from observed catch rates. An estimated 6,000 sharks were caught in this fishery during the study period.
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Campana, Steven E., Linda Marks, Warren Joyce, and Nancy E. Kohler. "Effects of recreational and commercial fishing on blue sharks (Prionace glauca) in Atlantic Canada, with inferences on the North Atlantic population." Canadian Journal of Fisheries and Aquatic Sciences 63, no. 3 (March 1, 2006): 670–82. http://dx.doi.org/10.1139/f05-251.
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The nominal catch of blue sharks (Prionace glauca) reported for the Canadian Atlantic grossly underestimates the annual catch mortality of about 1000 tonnes (t), making blue sharks the most frequently caught large shark in Canadian waters. Although blue sharks accounted for 99% of all sharks landed at recreational shark fishing tournaments, tournament catches accounted for only 3% of total fishing mortality. Standardized catch rate indices suggested a decline in blue shark abundance of about 5%6%·year1 since 1995. An increased mortality rate in recent years was suggested by a decline in the median size of blue sharks in the commercial catch. Two independent calculations suggest that North Atlantic catches exceeded 100 000 t, with catch mortalities ranging between 26 000 and 37 000 t. Because tagging studies indicated that blue sharks are highly migratory with a single population in the North Atlantic, the Canadian contribution to overall population mortality accounts for only 2% of the total. The fact that blue shark populations are relatively productive and resilient may help explain their persistence in the face of high international catch mortality and a decline in relative abundance.
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Daly-Engel, Toby S., R. Dean Grubbs, Brian W. Bowen, and Robert J. Toonen. "Frequency of multiple paternity in an unexploited tropical population of sandbar sharks (Carcharhinus plumbeus)." Canadian Journal of Fisheries and Aquatic Sciences 64, no. 2 (February 1, 2007): 198–204. http://dx.doi.org/10.1139/f07-005.
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Elasmobranch mating systems have received growing attention in the past few years because of worldwide overexploitation of shark populations. Few studies to date have examined mating systems in sharks because of difficulty in sampling. The sandbar shark (Carcharhinus plumbeus) is heavily harvested around the world and is the dominant species in the main commercial fishery for large coastal sharks in the United States. In contrast, Hawaii hosts one of the few unexploited populations of sandbar sharks and represents an opportunity to gather data on the reproductive biology of a vulnerable shark species without the confounding effects of fishing mortality. We examined the frequency of multiple paternity in Hawaiian sandbar sharks using 130 individuals (20 gravid females with three–eight pups each per litter) surveyed with six polymorphic microsatellite loci and determined that 8 of the 20 litters (40%) were multiple- sired. A Bayesian approach estimated the frequency of multiple mating in this population at 43.8%, with a 95% confidence interval of 23%–63%. We conclude that multiple paternity and genetic monogamy occur with roughly equal frequency in the Hawaiian sandbar shark population. This study may serve as groundwork for understanding the impact of commercial fishing pressure on elasmobranch mating systems.
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Cartamil, D., N. C. Wegner, S. Aalbers, C. A. Sepulveda, A. Baquero, and J. B. Graham. "Diel movement patterns and habitat preferences of the common thresher shark (Alopias vulpinus) in the Southern California Bight." Marine and Freshwater Research 61, no. 5 (2010): 596. http://dx.doi.org/10.1071/mf09153.
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The common thresher shark, Alopias vulpinus, is the basis of the largest commercial shark fishery in California waters. We used acoustic telemetry to determine the diel movement patterns and habitat preferences of this species in the Southern California Bight (SCB), where commercial fishing for the common thresher shark is concentrated. Eight common threshers (fork length: 122–203 cm) were tagged with temperature and depth-sensing acoustic transmitters and tracked for periods ranging from 22 to 49 h. Tracked sharks preferentially utilized deep offshore waters, and avoided shallower waters over the continental shelf. Mean rate of movement (ROM ± s.d.) was 2.15 ± 0.46 km h−1. ROM and angular concentration (r, a measure of relative linearity) both showed a strong daytime pattern, with highest values at dawn that decreased throughout the day, whereas nocturnal ROM and r were less variable. Daytime vertical movements consisted of either vertical excursions below the thermocline or relatively level swimming within the upper portion of the thermocline. Nocturnally, all sharks remained within the mixed layer. These findings suggest that the common thresher shark is primarily a daytime predator, and have relevance for estimating how the alteration of the set depth of fishing-gear could affect catch rates of this species in the SCB.
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Braccini, Matias, and Hilario Murua. "Quantifying shark and ray discards in Western Australia’s shark fisheries." Marine and Freshwater Research 73, no. 3 (November 9, 2021): 283–91. http://dx.doi.org/10.1071/mf21159.
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Commercial fisheries can discard a considerable volume of sharks and rays, which, as a group, are of high conservation concern. In Western Australia (WA), commercial shark fishing commenced in the 1940s; however, catch time series are not available for discarded species. The present study quantified catch (i.e. dead individuals) time series of discarded sharks and rays in WA’s shark fisheries using on-board observer information collected since 1993 and testing assumptions through sensitivity analysis. Overall, 18 shark and ray taxonomic groups were discarded, comprising ~20% of the observed catch by number. Port Jackson shark, southern eagle ray and spurdogs were the most commonly discarded elasmobranchs, followed by western wobbegong, angel sharks, stingrays, and guitarfish and shovelnose rays. For the base case scenario, the catch of these species was small, peaking at 12.6, 5.6, 1.3, 1.8, 4, 1.3 and 2.7 tonnes (Mg) respectively, given their low post-release mortality (PRM). Current catch levels were even lower (e.g. <5 Mg for Port Jackson shark). Other discarded elasmobranchs were rarely caught. Assuming 100% PRM resulted in higher annual catches, highlighting the need for further research on the PRM of sharks and rays. The reconstructed catch series will be used in risk assessments to determine the sustainability of discarded species.
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Francis, Malcolm P. "New Zealand shark fisheries: development, size and management." Marine and Freshwater Research 49, no. 7 (1998): 579. http://dx.doi.org/10.1071/mf97076.
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New Zealand’s shark fisheries have increased steadily since 1975 to reach 17 000–19 000 t per year. Commercial fisheries catch mainly spiny dogfish (Squalus acanthias), school shark (Galeorhinus galeus), skates (Raja nasuta and R. innominata), ghost sharks (Hydrolagus novaezealandiae and Hydrolagus sp.), rig (Mustelus lenticulatus) and elephantfish (Callorhinchus milii). School shark, rig and elephantfish fisheries have long histories, and catches are limited by Individual Transferable Quotas. Fisheries for spiny dogfish, skates and ghost sharks have only developed since 1979. Spiny dogfish and skate landings are partially regulated by total quotas. Other sharks are prohibited target species. Blue (Prionace glauca), porbeagle (Lamna nasus) and mako (Isurus oxyrinchus) sharks are taken as by-catch of the tuna longline fishery. There is a small recreational catch of spiny dogfish, school shark, rig, mako shark and blue shark. Historically important Maori fisheries for spiny dogfish, school shark and rig are now minor. A beach netting programme has operated off Dunedin beaches since 1969 to protect swimmers from shark attacks. Fisheries management measures include commercial quotas, prohibitions on target fishing many species, recreational bag limits, limits on set-net length, mesh size and soak time, and closure of many inshore waters to set-netting, trawling and Danish seining.
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Barnes, Michele L., John Lynham, Kolter Kalberg, and PingSun Leung. "Social networks and environmental outcomes." Proceedings of the National Academy of Sciences 113, no. 23 (May 23, 2016): 6466–71. http://dx.doi.org/10.1073/pnas.1523245113.
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Social networks can profoundly affect human behavior, which is the primary force driving environmental change. However, empirical evidence linking microlevel social interactions to large-scale environmental outcomes has remained scarce. Here, we leverage comprehensive data on information-sharing networks among large-scale commercial tuna fishers to examine how social networks relate to shark bycatch, a global environmental issue. We demonstrate that the tendency for fishers to primarily share information within their ethnic group creates segregated networks that are strongly correlated with shark bycatch. However, some fishers share information across ethnic lines, and examinations of their bycatch rates show that network contacts are more strongly related to fishing behaviors than ethnicity. Our findings indicate that social networks are tied to actions that can directly impact marine ecosystems, and that biases toward within-group ties may impede the diffusion of sustainable behaviors. Importantly, our analysis suggests that enhanced communication channels across segregated fisher groups could have prevented the incidental catch of over 46,000 sharks between 2008 and 2012 in a single commercial fishery.
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Walker, TI. "Fishery simulation model for sharks applied to the Gummy Shark, Mustelus antarcticus Gunther, from Southern Australian waters." Marine and Freshwater Research 43, no. 1 (1992): 195. http://dx.doi.org/10.1071/mf9920195.
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A dynamic pool simulation model is derived and applied to the gummy shark stock of the southern shark fishery. Inputs to the model are fishing effort reported by fishers for hooks and for gill-nets with mesh sizes of 6 inches (152 mm), 7 inches (178 mm) and 8 inches (203 mm) along with estimates for growth, natural mortality, catchability, hook and gill-net mesh selectivity, size at maturity and fecundity of females, sex ratio at birth, and length-weight relationships. Growth is described by the von Bertalanffy equation; hook selectivity is constant with length for sharks recruited to the fishery; gill-net selectivity is based on the probability density distribution of the gamma function where selectivity varies with the mesh size of the gill-nets and the length of the sharks; number of births is related to the proportion of females mature at each length, and the relationship between number of births and maternal weight is linear; parturition is annual and time is standardized so that parturition occurs at the beginning of each year; sex ratio at birth is based on observations of a 1: 1 sex ratio of embryos; and allometric weight-length is based on the power curve. Natural mortality of recruits, catchability, reproduction and growth parameters are held constant, but density-dependent natural mortality of prerecruits is varied in proportion to stock abundance. The model is used to simulate effects of historical longline fishing effort and gill-net fishing effort for each mesh size on stock biomass, numbers of sharks in the stock, and numbers of births. The performance of the model is evaluated by comparing simulated annual catches and the simulated mean weight of sharks captured with annual catches reported by the fishers and the mean weight of sharks sampled in commercial landings. Uncertainties surrounding estimates of some of the parameters are discussed. Notwithstanding its shortcomings, the model indicates that the stock of gummy shark has been severely reduced and is in danger of further depletion unless immediate action is taken to reduce the commercial catch.
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Agyeman, Narkie Akua, Carmen Blanco-Fernandez, Sophie Leonie Steinhaussen, Eva Garcia-Vazquez, and Gonzalo Machado-Schiaffino. "Illegal, Unreported, and Unregulated Fisheries Threatening Shark Conservation in African Waters Revealed from High Levels of Shark Mislabelling in Ghana." Genes 12, no. 7 (June 29, 2021): 1002. http://dx.doi.org/10.3390/genes12071002.
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Mislabelling of fish and fish products has attracted much attention over the last decades, following public awareness of the practice of substituting high-value with low-value fish in markets, restaurants, and processed seafood. In some cases, mislabelling includes illegal, unreported, and unregulated (IUU) fishing, contributing to overexploit substitute species that are undetectable when sold under wrong names. This is the first study of DNA barcoding to assess the level of mislabelling in fish marketed in Ghana, focusing on endangered shark species. Genetic identification was obtained from 650 base pair sequences within the cytochrome c oxidase I (COI) gene. All except one of 17 shark fillets analysed were wrongly labelled as compared with none of 28 samples of small commercial pelagic fish and 14 commercial shark samples purchased in Europe. Several substitute shark species in Ghana are endangered (Carcharhinus signatus and Isurus oxyrinchus) and critically endangered (Squatina aculeata). Shark products commercialized in Europe (n = 14) did not reveal mislabelling, thus specific shark mislabelling cannot be generalized. Although based on a limited number of samples and fish markets, the results that reveal trade of endangered sharks in Ghana markets encourage Ghanaian authorities to improve controls to enforce conservation measures.
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Chiaramonte, Gustavo E. "Shark fisheries in Argentina." Marine and Freshwater Research 49, no. 7 (1998): 601. http://dx.doi.org/10.1071/mf97136.
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In the Argentine Sea there are about 35 species of sharks. Three species are subjected to directed fishing: the smoothhound Mustelus schmitti, the school shark Galeorhinus galeus and the copper shark Carcharhinus brachyurus. Other species of elasmobranchs with commercial importance are the angel shark Squatina spp. and several species of skates and rays. The rise in chondrichthyan declared landings registered from 1988 to 1996 is due to the increase in landings of smoothhound and rays. The most important directed shark fishery in the South-West Atlantic is the Necochea gill-net fishery for school shark, which is carried out by the coastal fleet; details are given of the ships and the gill-nets used in this area. The length frequencies of the catches by gill-nets are presented for the school shark; fishing effort (length (km) of net in the water per ship per day) and CPUE (number of sharks per fishing effort) were found not to be good indicators of population trends in the school shark fishery. Resumen. En el Mar Argentino se han registrado 35 especies de tiburones. Tres de estas especies están sometidas a una pesca dirigida; el gatuzo, Mustelus schmitti, el cazón, tiburón vitamínico o trompa de cristal, Galeorhinus galeus y la bacota, Carcharhinus brachyurus. Otras especies de elasmobranquios de importancia comercial son el pez ángel Squatina spp. y algunas especies de rayas. El incremento en los desembarcos de condríctios declarados a las autoridades pesqueras entre 1988 y 1996 es debido principalmente al incremento del desembarco de gatuzo y rayas. La pesquería dirigida a tiburón más importante en el Atlántico Sudoccidental es la pesquería costera de enmalle de Necochea para el cazón. Se describen el largo de las embarcaciones y las redes utilizadas en el área (la medida de malla, el calado y la operación del arte de pesca). Se presenta la frecuencia del largo total de las capturas de cazón en redes de enmalle. Se halló para la pesquería del cazón que el esfuerzo pesquero (estimado como km de red en el agua por embarcación por día) y la CPUE (estimada como tiburones/esfuerzo de pesca) no son buenos indicadores de la tendencia en la abundancia poblacional.
11
Ryan, Karina L., Stephen M. Taylor, Rory McAuley, Gary Jackson, and Brett W. Molony. "Quantifying shark depredation events while commercial, charter and recreational fishing in Western Australia." Marine Policy 109 (November 2019): 103674. http://dx.doi.org/10.1016/j.marpol.2019.103674.
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Braccini, Matias, Simon de Lestang, and Rory McAuley. "Dusky sharks (Carcharhinus obscurus) undertake large-scale migrations between tropical and temperate ecosystems." Canadian Journal of Fisheries and Aquatic Sciences 75, no. 9 (September 2018): 1525–33. http://dx.doi.org/10.1139/cjfas-2017-0313.
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Understanding the large-scale migrations of marine predators can allow better representation of their population dynamics. The migration biology of dusky sharks (Carcharhinus obscurus), a cosmopolitan large marine predator with very low resilience to fishing, was quantified using a large-scale network of acoustic receivers deployed across Western Australia. Time-series plotting of individual shark detections and modified logistic modelling were used to determine the timing of acoustically tagged sharks’ seasonal migration, the proportion of the population migrating, and the size at which sharks start to migrate. Large (>200 cm fork length) dusky sharks migrated between areas closed (north) and open (south) to commercial shark fishing. There was limited evidence that smaller sharks occurred in the northern study area, whereas several larger individuals of both sexes undertook repeated north–south displacements, moving between disparate ecosystems within the Indian Ocean (21.7°S–35.4°S) and covering round-trip distances of 2000–3000 km per migratory event. For migrating individuals, the probability of occurring in the north was high in the austral winter–spring and low (males) to moderate (females) during the austral summer–autumn.
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Taylor, S. M., J. M. Braccini, B. D. Bruce, and R. B. McAuley. "Reconstructing Western Australian white shark (Carcharodon carcharias) catches based on interviews with fishers." Marine and Freshwater Research 69, no. 3 (2018): 366. http://dx.doi.org/10.1071/mf17140.
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The assessment of fisheries-related effects on protected species, such as white sharks (Carcharodon carcharias), is often hampered by a lack of historical catch information. In the present study, historical catch estimates derived from interviews with fishers operating in the Western Australian Temperate Demersal Gill-net and Demersal Longline Fisheries were matched with fishing effort data reported in statutory fishing returns. Catch estimates obtained from interviewed fishers were extrapolated to account for total catch in two different ways, resulting in mean (95% confidence intervals) estimates of 1232 (476–2245) and 1039 (505–2096) white sharks caught between 1988 and 2012. These estimates were then used to reconstruct catches over a 59-year period, from the start of commercial gillnetting in the mid-1950s. The reconstructed catch trend reflected the history of gill-net fishing effort, peaking in the late 1980s at a level approximately fourfold greater than the estimated catch of ~30 sharks year–1 in 2014. More than one-third of fishers interviewed expressed doubts about the accuracy of self-reported white shark catch data, a requirement of current legislation. Given the benefits of reporting data from protected species bycatch, efforts to accurately record this information should be continued and improved.
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Braccini, Matias, Brett Molony, and Nick Blay. "Patterns in abundance and size of sharks in northwestern Australia: cause for optimism." ICES Journal of Marine Science 77, no. 1 (October 10, 2019): 72–82. http://dx.doi.org/10.1093/icesjms/fsz187.
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Abstract Reliable information for population assessments is rare for sharks. We quantified patterns in catch rates and mean size for numerous tropical and subtropical species from 15 years of fishery-independent surveys (2002–2017) in northwestern Australia. This study region represents an area of ~0.8 million km2 which was closed to commercial shark fishing from 1993 or 2005 onward due to the very high State-wide catches of sandbar (Carcharhinus plumbeus) and dusky (Carcharhinus obscurus) sharks. A total of 43 shark and ray species were sampled, with sandbar shark being the most commonly caught species, followed by milk (Rhizoprionodon acutus), spot-tail (Carcharhinus sorrah), tiger (Galeocerdo cuvier), blacktip (Carcharhinus limbatus and Carcharhinus tilstoni), dusky and sliteye (Loxodon macrorhinus) sharks, and scalloped hammerhead (Sphyrna lewini). For sandbar shark, catch rates increased between 2008 and 2017 whereas for other taxa catch rates were mostly stable (albeit fluctuating). Mean size at capture fluctuated across years with no particular trends. Unlike for other parts of the world, catch rates and mean size of northwestern Australian sharks have been stable or increased in recent years. Though most shark species have conservative life histories, when science, management and enforcement work synergistically, sustainable resource use, recovery and conservation outcomes can all be achieved.
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Kroese, M., and W. H. H. Sauer. "Elasmobranch exploitation in Africa." Marine and Freshwater Research 49, no. 7 (1998): 573. http://dx.doi.org/10.1071/mf97122.
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The impact of fisheries on elasmobranchs in Africa is not well documented. Available data suggest that there are no large shark fishing nations (> 10000 t year-1), reported landings for 1994 being around 39 000 t. This value is believed to be a underestimate, because of a lack of data on catches and landings from the various different fishing methods and the large number of nations fishing in African waters. Existing data are mostly linked to industrial fisheries, although the artisanal sector could be responsible for substantial catches. Landed by-catch and discard rates of elasmobranchs are unknown for most commercial fisheries targeting teleosts. Limited data sources allowed only crude estimates of catch. The artisanal fishery is calculated to land a minimum of 20 000 t of sharks, whereas the industrial trawl sector is likely to catch 23 000 t. A conservative estimate for the African continent and the surrounding islands is ~95 000 t. The quality of catch-and-effort data for both commercial and subsistence fisheries on the African continent needs to be improved, and the by-catch issue should be investigated through trained onboard observers.
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Aditya, Zaka Firma, and Sholahuddin Al-Fatih. "PERLINDUNGAN HUKUM TERHADAP IKAN HIU DAN IKAN PARI UNTUK MENJAGA KESEIMBANGAN EKOSISTEM LAUT INDONESIA." Jurnal Ilmiah Hukum LEGALITY 24, no. 2 (February 28, 2017): 224. http://dx.doi.org/10.22219/jihl.v24i2.4273.
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The population of sharks and rays in Indonesia threatened with extinction. Based on the findings of WWF Indonesia that there are at least 10 million sharks caught in Indonesian waters each year for commercial purposes. Urgency of protection against sharks and stingrays are not only conservation activities related to efforts to save species of marine animals from extinction, but also related to global environmental issues. Until this time there has been no regulation of the Indonesian government, which specifically provides protection to the conservation of sharks and rays in Indonesia’s marine waters. In this paper, the author will discuss two findings. First, the lack of regulations that provide legal protection to sharks and stingrays from illegal fishing activity. Secondly, there are two efforts can be made by the government, repressive and preventive measures. A repressive measure carried out by law enforcement with a very heavy sanction the perpetrators of fishing of sharks and stingrays. Preventive efforts done by making shark conservation areas and through education and awareness to the community.
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McAuley, Rory B., Colin A. Simpfendorfer, and Norm G. Hall. "A method for evaluating the impacts of fishing mortality and stochastic influences on the demography of two long-lived shark stocks." ICES Journal of Marine Science 64, no. 9 (September 20, 2007): 1710–22. http://dx.doi.org/10.1093/icesjms/fsm146.
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Abstract McAuley, R. B., Simpfendorfer, C. A., and Hall, N. G. 2007. A method for evaluating the impacts of fishing mortality and stochastic influences on the demography of two long-lived shark stocks. — ICES Journal of Marine Science, 64. Stochastic demographic models were developed for Carcharhinus obscurus and C. plumbeus populations off the west coast of Australia by resampling the input parameters for life tables from empirical biological data collected from commercial target fisheries and fishery-independent surveys. The models were used to examine the effects of multiple scenarios of age-specific survival, derived from the fishing mortality rates estimated from a tagging study on sharks and indirect estimates of natural mortality. In the absence of fishing, median estimates of the rates of intrinsic population increase (r) were 0.025 for both species. Inclusion of the age-specific fishing mortality rates estimated for C. obscurus recruits born in 1994 and 1995 resulted in the median estimates of r declining to 0.007 and 0.012, respectively, suggesting that recent harvest levels of mainly neonates by the target fishery were probably sustainable. However, the model also suggested that the population was more susceptible to exploitation of older sharks than was previously believed. The C. plumbeus model indicated that fishing mortality between 2001 and 2004 was probably unsustainable. The increasingly negative trend in median r estimates (from –0.032 to –0.049), and the population’s apparently limited capacity for density-dependent compensation through changes in fecundity, somatic growth and longevity, suggests that management intervention is necessary to prevent continued stock depletion.
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Raoult, V., V. Peddemors, and J. E. Williamson. "Biology of angel sharks (Squatina sp.) and sawsharks (Pristiophorus sp.) caught in south-eastern Australian trawl fisheries and the New South Wales shark-meshing (bather-protection) program." Marine and Freshwater Research 68, no. 2 (2017): 207. http://dx.doi.org/10.1071/mf15369.
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Two species of angel shark (Squatina australis, S. albipunctata) and two species of sawshark (Pristiophorus nudipinnis, P. cirratus) are frequently caught in south-eastern Australia. Little is known of the biology of these elasmobranchs, despite being caught as secondary target species in large numbers. The present study collected morphometric and reproductive data from sharks caught in shark-control nets, commercial fishing trawlers and research trawlers in south-eastern Australia. All four species had female-biased sexual size dimorphism, but growth curves between sexes did not differ. Male S. australis individuals were fully mature at ~800-mm total length, male P. nudipinnis at ~900mm, and male P. cirratus at ~800mm. Anterior pectoral margins could be used to determine total length in all species. No morphometric measurement could reliably separate Squatina spp. or Pristiophorus spp., although S. albipunctata over 1000-mm total length had larger eyes than did S. australis.
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da Silva, Thaísy Emmanuelle Florentino, Rosangela Lessa, and Francisco Marcante Santana. "Current knowledge on biology, fishing and conservation of the blue shark (Prionace glauca)." Neotropical Biology and Conservation 16, no. 1 (January 21, 2021): 71–88. http://dx.doi.org/10.3897/neotropical.16.e58691.
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The blue shark (Prionace glauca) is a large predator in marine ecosystems, figuring as the most common and abundant species in oceanic fisheries. For this reason, many studies on this species were conducted throughout its entire distribution range. However, no comparison has been made regarding the variability of the aspects addressed herein. Thus, the present study aims at analyzing the available information on P. glauca. This species constitutes between 85 and 90% of the total elasmobranchs caught by oceanic fisheries with pelagic longlines. Growth parameters reveal that individuals in the Atlantic Ocean show the highest asymptotic lengths when compared to those found in other oceans. Females present an average uterine fecundity of 30 embryos. Although it shows a diverse diet, it is mainly composed of teleost fish and cephalopods. Currently, the main threat to the species is commercial fishing, being listed in Brazil and worldwide, according to IUCN as Near Threatened. Regardless, information on crucial aspects, such as its population dynamics, are still scarce or unreliable for many areas. Despite the number of studies regarding its distribution, abundance, and biology, data for new stock assessments of P. glauca are still needed to improve the species’ management.
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Holts, DB, and DW Bedford. "Horizontal and vertical movements of the shortfin mako shark, Isurus oxyrinchus, in the Southern California Bight." Marine and Freshwater Research 44, no. 6 (1993): 901. http://dx.doi.org/10.1071/mf9930901.
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Recreational and commercial fishing effort directed at the shortfin mako shark, Isurus oxyrinchus, off the coast of southern California increased markedly in the mid 1980s. However, very little is known about the population size, stock structure or movements of these sharks in the northern Pacific. It is important to determine their role in these waters because the southern California bight may be an important pupping and nursery area for shortfin mako sharks. Acoustic telemetry was used to identify short-term horizontal and vertical movements of three shortfin mako sharks in the southern California bight during the summer of 1989. All three sharks were two-year-old juveniles and were tracked for periods of from 18 to 25 h. They spent 90% of their time in the mixed layer, with only infrequent excursions below the thermocline. Vertical and horizontal movements did not indicate any diel activity pattern associated with distance to the shore or nearby islands or with bottom topography.
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Moran, M., C. Burton, and J. Jenke. "Long-term movement patterns of continental shelf and inner gulf snapper (Pagrus auratus, Sparidae) from tagging in the Shark Bay region of Western Australia." Marine and Freshwater Research 54, no. 8 (2003): 913. http://dx.doi.org/10.1071/mf03012.
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Snapper is an important commercial and recreational target species in the Shark Bay region of Western Australia. The present study aimed to define the range of movements of snapper by tagging in the two inner gulfs of Shark Bay and on oceanic fishing grounds adjacent to the Bay. Recaptures by fishers fell to low levels within 4 years after tagging, but small numbers of recaptures were still being made up to 15 years after release. There was no mixing of snapper populations between the two inner gulfs nor was there any movement between the ocean and the inner bay. This supports genetic and other evidence for the existence of several separate stocks in the region. Snapper of the ocean stock were mostly recaptured within 20 km of their release point, although a few fish moved long distances of up to 370 km southwards along the continental shelf. The tagged snapper tended to become more dispersed along the shelf with increasing years at liberty. Yet, an empirical model indicated that of the snapper recruiting to the main oceanic fishing grounds near Koks Island, which have a mean life expectancy in the fishery of 1.5 years, 76% would remain within 93 km (50 nautical miles), even after 6 years. The distinct stocks and their movement characteristics are significant for snapper fishery management in the Shark Bay region.
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Dunbrack, Robert, and Robert Zielinski. "Body Size Distribution and Frequency of Anthropogenic Injuries of Bluntnose Sixgill Sharks, Hexanchus griseus, at Flora Islets, British Columbia." Canadian Field-Naturalist 119, no. 4 (October 1, 2005): 537. http://dx.doi.org/10.22621/cfn.v119i4.184.
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The Bluntnose Sixgill Shark (Hexanchus griseus) is a widely distributed demersal species whose population biology is poorly understood. Although H. griseus is normally found in deep continental slope waters, individuals from a population in the Strait of Georgia, British Columbia, make unexpected diurnal movements onto a shallow reef (Flora Islets) between June and August. This shallow water activity allowed in situ length measurements to be made on 35 free-swimming Bluntnose Sixgill Sharks using stereo videography. The measured sharks were all large juveniles and sub-adults, although smaller juveniles and pregnant females are known to occur in deeper adjacent waters. The restricted size distribution at Flora Islets may arise because small juveniles avoid contact with larger conspecifics and mating takes place offshore. All measured sharks were individually identified by unique scar patterns. In 13 of 35 sharks these scars were consistent with injuries expected from hooking and entanglement by commercial fishing gear.
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Jaiteh, Vanessa F., Simon J. Allen, Jessica J. Meeuwig, and Neil R. Loneragan. "Combining in-trawl video with observer coverage improves understanding of protected and vulnerable species by-catch in trawl fisheries." Marine and Freshwater Research 65, no. 9 (2014): 830. http://dx.doi.org/10.1071/mf13130.
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Assessments of incidental wildlife mortality resulting from fishing rarely account for unobserved by-catch. We assessed by-catch of protected and vulnerable wildlife species in an Australian trawl fishery by comparing in-trawl video footage with data collected by an on-board observer. Data were obtained from 44 commercial trawls with two different by-catch reduction devices (BRDs). Eighty-six individuals from six major taxa (dolphins, sharks, rays, sea snakes, turtles and sygnathids) were documented from video analysis, including the endangered scalloped hammerhead shark (Sphyrna lewini) and the critically endangered green sawfish (Pristis zijsron). On the basis of the 2008–2009 fishing effort of 4149 trawls and scaling from these results, we estimated the annual catch of protected and vulnerable species (± 1 s.e.) at 8109 ± 910 individuals. Only 34% of by-catch was expelled through the BRDs. Independent observer data for the 44 trawls showed that 77% of the landed by-catch from these taxa were dead when discarded. The results indicate that unaccounted by-catch in trawl fisheries can be substantial, and that current methods of recording by-catch on-board vessels are likely to underestimate total fishing mortality. We recommend gear modifications and their validation through dedicated observer coverage, combined with in-trawl video camera deployments to improve current approaches to by-catch mitigation.
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Whitney, Nicholas M., Karissa O. Lear, John J. Morris, Robert E. Hueter, John K. Carlson, and Heather M. Marshall. "Connecting post-release mortality to the physiological stress response of large coastal sharks in a commercial longline fishery." PLOS ONE 16, no. 9 (September 15, 2021): e0255673. http://dx.doi.org/10.1371/journal.pone.0255673.
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Bycatch mortality is a major factor contributing to shark population declines. Post-release mortality (PRM) is particularly difficult to quantify, limiting the accuracy of stock assessments. We paired blood-stress physiology with animal-borne accelerometers to quantify PRM rates of sharks caught in a commercial bottom longline fishery. Blood was sampled from the same individuals that were tagged, providing direct correlation between stress physiology and animal fate for sandbar (Carcharhinus plumbeus, N = 130), blacktip (C. limbatus, N = 105), tiger (Galeocerdo cuvier, N = 52), spinner (C. brevipinna, N = 14), and bull sharks (C. leucas, N = 14). PRM rates ranged from 2% and 3% PRM in tiger and sandbar sharks to 42% and 71% PRM in blacktip and spinner sharks, respectively. Decision trees based on blood values predicted mortality with >67% accuracy in blacktip and spinner sharks, and >99% accuracy in sandbar sharks. Ninety percent of PRM occurred within 5 h after release and 59% within 2 h. Blood physiology indicated that PRM was primarily associated with acidosis and increases in plasma potassium levels. Total fishing mortality reached 62% for blacktip and 89% for spinner sharks, which may be under-estimates given that some soak times were shortened to focus on PRM. Our findings suggest that no-take regulations may be beneficial for sandbar, tiger, and bull sharks, but less effective for more susceptible species such as blacktip and spinner sharks.
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Peddemors, V. M. "Delphinids of southern Africa: A review of their distribution, status and life history." J. Cetacean Res. Manage. 1, no. 2 (January 25, 2023): 157–65. http://dx.doi.org/10.47536/jcrm.v1i2.463.
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Eighteen species of delphinids have been recorded from Africa, south of l 7°S. This review includes analyses of the distribution and status, life history and feeding habits for each species, primarily using published data from strandings, incidentally caught animals and sightings. Although there is little known for most of the species distributed over the continental shelf, it appears that there is presently little human-induced threat to these. However, more research emphasis should in future be placed on possible detrimental interactions due to overfishing of delphinid prey stocks. Increased commercial fishing pressure will inevitably also increase interactions between the fishery and the affected delphinids. Only three inshore species are presently considered to be vulnerable: Heaviside's dolphins (Cephalorhynchus heavisidil), bottlenose dolphins (Tursiops truncatus) in KwaZulu-Natal and Namibia, and Inda-Pacific hump-backed dolphins (Sousa chinensis) in KwaZulu-Natal. Heaviside's dolphins are endemic and, although presently probably able to sustain mortalities following interactions with commercial fishing gear, may become negatively impacted should fishing activities increase. The bottlenose dolphin population in Namibia appears localised in its distribution and may therefore also be vulnerable to any future coastal development or commercial fishery expansions, while in KwaZulu-Natal they are subjected to ongoing incidental catches in shark nets, heavy pollution levels, habitat destruction and increased competition with fishermen for limited food resources. In KwaZulu-Natal, Inda-Pacific hump-backed dolphins are subjected to the same pressures as experienced by bottlenose dolphins, albeit more severely, while in Mozambique it is occasionally caught incidentally in gillnets or in a targeted fishery. Although generally considered an offshore species, southern right whale dolphins (Lissodelphis peronii) also appears to be extremely localised in distribution within southern Africa, and any future planned expansion of commercial driftnet fisheries off Namibia should be carefully monitored for incidental catches which may impact this population.
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Mueller, Ute, Mervi Kangas, Errol Sporer, and Nick Caputi. "Variability in the spatial and temporal distribution of the saucer scallop, Amusium balloti, in Shark Bay - management implications." Marine and Freshwater Research 63, no. 11 (2012): 1152. http://dx.doi.org/10.1071/mf12051.
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The present paper is the first description using geostatistical modelling of recruitment (0+) and residual (1+) scallop variability from an annual survey in a semi-tropical embayment. Geostatistical modelling provides a useful tool to explore and interpret distribution patterns and can provide information to determine potential behaviour of fishers. It may also aid in determining the time it will take from the beginning of the season to reach a catch-rate threshold, which is the management strategy implemented in the Shark Bay scallop fishery since 2004. High variability in recruit abundance and spatial distribution was observed among years, whereas patterns of residual abundance and distribution were less variable because of the fishing patterns of both the scallop and prawn fleets. Comparisons of commercial catch patterns indicated that high survey-abundance areas correlate with higher catches, validating that survey results are a good tool for fishers to utilise to target their fishing practices to optimise and maximise catch efficiencies. The study highlighted the inherent annual variability of scallop recruitment abundance and distribution that are primarily considered to be environmentally driven. However, both recruits and residual scallops contribute to the whole catch, so retaining residual scallops from year to year is important.
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Briton, Florence, Olivier Thébaud, Claire Macher, Caleb Gardner, and Lorne Richard Little. "Flexibility of joint production in mixed fisheries and implications for management." ICES Journal of Marine Science 78, no. 5 (April 14, 2021): 1599–613. http://dx.doi.org/10.1093/icesjms/fsab057.
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Abstract Over the past decade, efforts have been made to factor technical interactions into management recommendations for mixed fisheries. Yet, the dynamics underlying joint production in mixed fisheries are generally poorly captured in operational mixed fisheries models supporting total allowable catch advice. Using an integrated ecological–economic simulation model, we explore the extent to which fishers are likely to alter the species composition of their landings in a mixed fishery managed with individual transferable quotas, the Australian Southern and Eastern Scalefish and Shark Fishery. Our simulations capture three different types of joint production problems, highlighting the flexibility that exists in terms of achievable catch compositions when quota markets provide the economic incentives to adapt fishing practices to quota availability. These results highlight the importance of capturing the drivers of fishing choices when advising TAC decisions in mixed fisheries. We also identify a hierarchy of species in this fishery, with harvest targets set for primary commercial species determining most of its socio-economic performance.
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McMillan, Matthew N., Christopher Izzo, Claudia Junge, Ole Thomas Albert, Armelle Jung, and Bronwyn M. Gillanders. "Analysis of vertebral chemistry to assess stock structure in a deep-sea shark, Etmopterus spinax." ICES Journal of Marine Science 74, no. 3 (October 27, 2016): 793–803. http://dx.doi.org/10.1093/icesjms/fsw176.
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Deep-sea sharks play a valuable ecological role helping maintain food web balance, yet they are vulnerable to commercial fishing because of slow growth rates and low reproductive capacity. Overfishing of sharks can heavily impact marine ecosystems and the fisheries these support. Knowledge of stock structure is integral to sustainable management of fisheries. The present study analysed vertebral chemistry using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to assay concentrations of 7Li, 23Na, 24Mg, 55Mn, 59Co, 60Ni, 63Cu, 66Zn, 85Rb, 88Sr, 138Ba and 208Pb to assess stock structure in a deep-sea shark, Etmopterus spinax, in Norwegian and French waters. Few studies have applied this technique to elasmobranch vertebrae and the present study represents its first application to a deep-sea shark. Three stocks were identified at the regional scale off western Norway, southern Norway, and France. At finer spatial scales there was evidence of strong population mixing. Overall, the general pattern of stock structure outlined herein provides some indication of the spatial scales at which stocks should be viewed as distinct fisheries management units. The identification of an effective multi-element signature for distinguishing E. spinax stocks utilizing Sr, Ba, Mg, Zn and Pb and the methodological groundwork laid in the present study could also expedite future research into stock structure for E. spinax and deep-sea elasmobranchs more generally.
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Moura, Teresa, Mónica C. Silva, Ivone Figueiredo, Ana Neves, Pablo Durán Muñoz, Maria Manuela Coelho, and Leonel S. Gordo. "Molecular barcoding of north-east Atlantic deep-water sharks: species identification and application to fisheries management and conservation." Marine and Freshwater Research 59, no. 3 (2008): 214. http://dx.doi.org/10.1071/mf07192.
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Two genera of elasmobranchii, Centrophorus and Centroscymnus, include species that represent the highest landings of deep-water sharks caught by fishing fleets operating in the north-east Atlantic. There are morphology-based identification problems among and within genera, and landings of processed shark products further prevent an objective assessment of these species. The present study is the first attempt to test the suitability of using a DNA barcode approach to discriminate accurately among the four most important commercial deep-water shark species: Centrophorus squamosus, Centrophorus granulosus, Centroscymnus coelolepis and, recently discovered in Portuguese ports, Centroscymnus owstoni. Sequence analyses of the mitochondrial DNA cytochrome c oxidase subunit I (COI) gene revealed low levels of haplotypic and genetic diversities. Higher levels of inter-specific relative to intra-specific divergences allowed discrimination among species, which form reciprocally monophyletic clades. Inclusion of published COI sequences from other species within the same genera revealed haplotype sharing among species, which calls into question the current taxonomy and accuracy of fisheries data available. Amplification of the COI gene coupled with MboI restriction digests was found to be a fast and inexpensive strategy to resolve within genera identification problems. Molecular barcoding constitutes a critical tool for the assessment and implementation of urgent management policies for this group of species.
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Musyl, Michael K., and Eric L. Gilman. "Post-release fishing mortality of blue (Prionace glauca) and silky shark (Carcharhinus falciformes) from a Palauan-based commercial longline fishery." Reviews in Fish Biology and Fisheries 28, no. 3 (March 19, 2018): 567–86. http://dx.doi.org/10.1007/s11160-018-9517-2.
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Graham, K. J., N. L. Andrew, and K. E. Hodgson. "Changes in relative abundance of sharks and rays on Australian South East Fishery trawl grounds after twenty years of fishing." Marine and Freshwater Research 52, no. 4 (2001): 549. http://dx.doi.org/10.1071/mf99174.
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Upper continental slope trawling grounds (200–650 m depth) off New South Wales were surveyed with the same vessel and trawl gear and similar sampling protocols in 1976–77 (during the early years of commercial exploitation) and in 1996–97. The 1996–97 mean catch rate of sharks and rays, pooled for the main 15 species (or species groups), was ~20% of the 1976–77 mean. Individual catch rates were substantially lower in 1996–97 for 13 of the 15 species or species groups. The greatest decline was observed for dogsharks of the genus Centrophorus, which were most abundant in 1976–77 but rarely caught 20 years later. In contrast, 1996–97 catch rates of spiky dogshark (Squalus megalops) and, to a lesser extent, whitefin swell shark (Cephaloscyllium sp. A) were similar to those in 1976–77. Trawling during 1979–81 provided data for nine species, albeit not corrected for larger gear size, and the pooled mean catch rate for sharks and rays in the depth range 300–525 m was ~28% of the mean for 1976–77. The results suggest that the biomass of most species of sharks and rays declined rapidly as the fishery developed and is now at very low levels.
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Klaer, N. L. "Steam trawl catches from south-eastern Australia from 1918 to 1957: trends in catch rates and species composition." Marine and Freshwater Research 52, no. 4 (2001): 399. http://dx.doi.org/10.1071/mf00101.
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Haul-by-haul steam trawler catch and effort data for 1918–23, 1937–43 and 1952–57, which cover a large portion of the history of steam trawling in the Australian South East Fishery, were examined in detail for the first time. There were 64371 haul records in total. The catch-rate for all retained catch combined shows a strong decline overall, with a brief recovery during World War II, probably due to increased retention of previously discarded species. The fishing fleet moved to more distant fishing grounds and deeper waters as the catch-rate declined. The catch-rates of the main commercial species followed a similar pattern in a number of regions within the fishery. The catch-rate of the primary target species – tiger flathead (Neoplatycephalus richardsoni) – dropped considerably from the early, very high, catch-rates. Chinaman leatherjacket (Nelusetta ayraudi) and latchet (Pterygotrigla polyommata) – species that were apparently abundant in the early years of the fishery, virtually disappeared from catches in later years. The appearance of greater catches of jackass morwong (Nemadactylus macropterus), redfish (Centroberyx affinis) and shark/skate during the war and afterwards was probably due to increased retention of catches of these species. The disappearance of certain species from the catch may be due to high fishing pressure alone, or to a combination of fishing pressure, changes in the shelf habitat possibly caused by the trawl gear, and environmental fluctuations.
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Jerome, J. M., A. J. Gallagher, S. J. Cooke, and N. Hammerschlag. "Integrating reflexes with physiological measures to evaluate coastal shark stress response to capture." ICES Journal of Marine Science 75, no. 2 (November 2, 2017): 796–804. http://dx.doi.org/10.1093/icesjms/fsx191.
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Abstract In both commercial and recreational fisheries, sharks are captured and released alive to comply with regulations or due to low economic value or voluntary conservation ethic. As a result, understanding the physiological and behavioural responses of sharks to capture stress is important for determining subsequent effects of fisheries interactions on a species-specific basis, as well as for identifying factors that influence mortality. Here, we employed a suite of conventional blood physiology endpoints (glucose, lactate, and haematocrit) integrated with assessments of reflex impairment on blacktip (Carcharhinus limbatus), great hammerhead (Sphyrna mokarran), nurse (Ginglymostoma cirratum) and sandbar sharks (Carcharhinus plumbeus) captured via experimental drumline gear. We documented a wide range of species-specific differences in all parameters assessed, with nurse sharks consistently having the lowest relative levels of physiological disturbance and reflex impairment; and with great hammerheads exhibiting the highest level of physiological disturbance and reflex impairment, suggesting higher vulnerability to fishing. In general, increases in lactate were positively associated with hook time and correlated with reflex impairment assessment. Moreover, reflex indices showed significant impairment with hook time, with the “jaw” reflex emerging as the most potential predictor of disturbance. Our study results connect previously reported species-specific at-vessel and post-release mortality rates to their physiological disturbance and reflex impairment.
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Rosello, Mercedes, Juan Vilata, and Dyhia Belhabib. "Atlantic Shortfin Mako: Chronicle of a Death Foretold?" Laws 10, no. 3 (June 23, 2021): 52. http://dx.doi.org/10.3390/laws10030052.
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This article outlines recent events concerning the conservation and management trajectory of a highly migratory shark species, the shortfin mako (Isurus oxyrinchus), in the North Atlantic, where it has been routinely captured recreationally and as part of commercial fishing operations alongside other species. Noting recent warnings concerning the high mortality of the species in this ocean region, and the threat of imminent population collapse, this article sets out a number of applicable law of the sea provisions, and carries out an evaluation of relevant measures for target and incidental capture species, discussing their applicability to the mako fishery. It also presents an analysis of regional and global governance actions taken to date by the international community and by individual actors, noting a number of shortfalls, and outlining potential responses.
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Estupiñán-Montaño, Colombo, Luis Cedeño-Figueroa, José F. Estupiñán-Ortiz, Felipe Galván-Magaña, Alejandro Sandoval-Londoño, David Castañeda-Suarez, and Carlos J. Polo-Silva. "Feeding habits and trophic level of the smooth hammerhead shark, Sphyrna zygaena (Carcharhiniformes: Sphyrnidae), off Ecuador." Journal of the Marine Biological Association of the United Kingdom 99, no. 3 (July 13, 2018): 673–80. http://dx.doi.org/10.1017/s0025315418000474.
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As apex predators, sharks are known to play an important role in marine food webs. Detailed information on their diet and trophic level is however needed to make clear inferences about their role in the ecosystem. A total of 335 stomachs of smooth hammerhead sharks, Sphyrna zygaena, were obtained from commercial fishing vessels operating in the Ecuadorian Pacific between January and December 2004. A total of 53 prey items were found in the stomachs. According to the Index of Relative Importance (%IRI), cephalopods were the main prey (Dosidicus gigas, Sthenoteuthis oualaniensis, Ancistrocheirus lesueurii and Lolliguncula [Loliolopsis] diomedeae). Sphyrna zygaena was thus confirmed to be a teutophagous species. The estimated trophic level of S. zygaena was between 4.6 and 5.1 (mean ± SD: 4.7 ± 0.16; males: 4.7; females: 4.8). Levin's index (BA) was low (overall: 0.07; males: 0.08; females: 0.09), indicating a narrow trophic niche. We found that sharks <150 cm in total length consumed prey of coastal origin, whereas sharks ≥150 cm foraged in oceanic waters and near the continental shelf. The analyses indicate that S. zygaena is a specialized predator consuming mainly squids.
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Veríssimo, A., J. R. McDowell, and J. E. Graves. "Genetic population structure and connectivity in a commercially exploited and wide-ranging deepwater shark, the leafscale gulper (Centrophorus squamosus)." Marine and Freshwater Research 63, no. 6 (2012): 505. http://dx.doi.org/10.1071/mf11237.
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The leafscale gulper (Centrophorus squamosus) is a wide-ranging deepwater benthopelagic shark threatened by commercial fisheries in parts of its range. Despite concerns about resource sustainability, little is known about the population structure and connectivity between critical habitats of the leafscale gulper. This study investigates the genetic population structure and the migration patterns of C. squamosus using nuclear microsatellites and mitochondrial NADH dehydrogenase subunit 2 (ND2) gene sequences. Genetic diversity was estimated and compared among sample collections from off Ireland, Portugal, the Azores, South Africa and New Zealand. The null hypothesis of genetic homogeneity among all collections was not rejected by the nuclear loci (FST (the overall genetic differentiation among sample collections) = –0.002, P = 0.88), but we found long-term genetic divergence between New Zealand and the remaining collections at the mtDNA ND2 (FCT (genetic differentation among groups of sample collections) = 0.366, P = 0.000). Migration rate estimates indicated limited female dispersal across the Indian Ocean whereas males showed less restricted dispersal. Our results are consistent with a single genetic stock of C. squamosus and the existence of sex-biased dispersal across the Indian Ocean. Widespread genetic homogeneity at nuclear loci minimizes the loss of unique adaptive genetic diversity in the event of localised depletion. However, high local fishing mortality may have far reaching impacts given the marked sex- and maturity-stage-based habitat partitioning previously reported for C. squamosus.
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Echwikhi, K., B. Saidi, and M. N. Bradai. "Elasmobranchs longline fisheries in the Gulf of Gabès (southern Tunisia)." Journal of the Marine Biological Association of the United Kingdom 94, no. 1 (September 10, 2013): 203–10. http://dx.doi.org/10.1017/s0025315413000726.
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In Tunisia, elasmobranch landings have decreased substantially in recent years. Generally, species-specific information is largely unavailable for artisanal fisheries, but it is essential to increase knowledge and to ensure proper management of these species. This study analysed elasmobranch catches with longline fishery in the Gulf of Gabès. In total, 21 and 20 pelagic and bottom longline fishing trips were conducted, respectively, from July to September in 2007 and 2008. A total of eight elasmobranch species were caught: four batoids and four sharks. Pelagic longline captures were hooked externally while a high number of individuals captured with bottom longline were hooked internally. Discards due essentially to low commercial value and size represented 7.6% of total number of elasmobranch specimens caught. Longline landings in the Gulf of Gabès were principally composed of sandbar shark, Carcharhinus plumbeus, representing, respectively, 94.14% and 21.17% in number of pelagic and bottom longline captures. The importance of rhinobatids and Mustelus capture with bottom longline reflect their abundance in this area compared to other Mediterranean zones. Juveniles, including neonates with umbilical scars, dominated carcharhnids specimens, while smoothhound and guitarfish captures were dominated by mature individuals. Mitigation measures based on gear modifications, size limits and delineated nursery areas in the Gulf of Gabès should be developed to protect these vulnerable species.
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Gračan, Romana, Scott A. Heppell, Gordana Lacković, and Bojan Lazar. "Age and growth dynamics of spiny dogfish, Squalus acanthias, in the Adriatic Sea (Eastern Mediterranean Sea)." Marine and Freshwater Research 67, no. 3 (2016): 357. http://dx.doi.org/10.1071/mf14116.
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This research provides the first information on age and growth estimates for the endangered Mediterranean subpopulation of spiny dogfish, a commercially exploited shark, highly sensitive to overexploitation. We collected samples from 206 specimens caught by commercial bottom trawls in the Adriatic Sea, and utilising three ageing protocols achieved good agreement between the readings (average percentage error=1.65%). Four growth models were fitted to length-at-age and weight-at-age data, for each sex separately. The Gompertz growth model produced the statistically best fit resulting in the following parameters: k values for males and females were 0.09 and 0.04 year–1, size-at-birth ranged from 22.9 to 24.1-cm total length, with a theoretical asymptotic length of 103.3cm for males and 173.3cm for females. The age at 50% maturity was 10.5 years for males and 20.1 years for females. The maximum age was estimated at 23 years for males and 36 years for females, with natural mortality estimates of 0.12 for males and 0.07 for females. As a result of reported demographic parameter estimates, high fishing effort and particularly low resilience of the species to exploitation, it is important to produce proper species-specific management strategy for the spiny dogfish in the region.
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Otero-Pérez, Rafael, María Permuy, Estefanía López-Senra, Miriam López-Álvarez, Mónica López-Peña, Julia Serra, Antonio González-Cantalapiedra, Fernando M. Muñoz, and Pío González. "Preclinical Evaluation of an Innovative Bone Graft of Marine Origin for the Treatment of Critical-Sized Bone Defects in an Animal Model." Applied Sciences 11, no. 5 (February 27, 2021): 2116. http://dx.doi.org/10.3390/app11052116.
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Autogenous cancellous bone graft is the current gold standard of treatment for the management of bone defects since it possesses the properties of osteoinduction, osteoconduction, and osteogenesis. Xenografts and synthetic grafts have been widely reported as available and low-cost alternatives, which retain good osteoconductive and mechanical properties. Given the rich biodiversity of ocean organisms, marine sources are of particular interest in the search for alternative bone grafts with enhanced functionalities. The purpose of this paper is to assess the biocompatibility of a marine-derived bone graft obtained from shark tooth, which is an environmentally sustainable and abundant raw material from fishing. This research presents the findings of a preclinical trial—following UNE-EN ISO 10993—that induced a critical-sized bone defect in a rabbit model and compared the results with a commercial bovine-derived bone graft. Evaluation by micro-computed tomography and histomorphometric analysis 12 weeks after implantation revealed good osseointegration, with no signs of inflammatory foreign body reactions, fibrosis, or necrosis in any of the cases. The shark tooth-derived bone graft yielded significantly higher new bone mineral density values (54 ± 6%) than the control (27 ± 8%). Moreover, the percentage of intersection values were much higher (86 ± 8%) than the bovine-derived bone graft (30 ± 1%) used as control. The area of occupancy by bone tissue in the test material (38 ± 5%) also gave higher values than the control (30 ± 6%). The role of physicochemical properties, biphasic structure, and composition on the stimulation of bone regeneration is also discussed.
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Carvalho, Fernando P., João M. Oliveira, and Margarida Malta. "Radionuclides in deep-sea fish and other organisms from the North Atlantic Ocean." ICES Journal of Marine Science 68, no. 2 (July 30, 2010): 333–40. http://dx.doi.org/10.1093/icesjms/fsq088.
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Abstract Carvalho, F. P., Oliveira, J. M., and Malta, M. 2011. Radionuclides in deep-sea fish and other organisms from the North Atlantic Ocean – ICES Journal of Marine Science, 68: 333–340. The naturally occurring radionuclides potassium-40 (40K), radium-226 (226Ra), polonium-210 (210Po), and lead-210 (210Pb) were measured in commercial fish species such as cod, halibut, redfish, and shark from several fishing grounds in the North Atlantic, as well as the anthropogenic radionuclides caesium-137 (137Cs) and plutonium isotopes (238Pu and 239+240Pu). The concentrations of naturally occurring radionuclides were compared with those of anthropogenic origin. The main contributors to the radiation dose were 210Po and 40K, with anthropogenic radionuclides accounting for just a small contribution. We provide the first measurements of naturally occurring radionuclides in abyssal organisms, including fish, molluscs, and crustaceans, from the Porcupine Abyssal Plain. In these organisms, radionuclide concentrations and the absorbed radiation doses were dominated by 210Po and were comparable with those determined in related coastal species, confirming that the deep-sea fauna do not live in an environment protected from ionizing radiation. Absorbed radiation doses from naturally occurring radionuclides still exceed radiation doses caused by anthropogenic radionuclides introduced into the Northeast Atlantic.
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Byrne, Michael E., Enric Cortés, Jeremy J. Vaudo, Guy C. McN Harvey, Mark Sampson, Bradley M. Wetherbee, and Mahmood Shivji. "Satellite telemetry reveals higher fishing mortality rates than previously estimated, suggesting overfishing of an apex marine predator." Proceedings of the Royal Society B: Biological Sciences 284, no. 1860 (August 2, 2017): 20170658. http://dx.doi.org/10.1098/rspb.2017.0658.
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Overfishing is a primary cause of population declines for many shark species of conservation concern. However, means of obtaining information on fishery interactions and mortality, necessary for the development of successful conservation strategies, are often fisheries-dependent and of questionable quality for many species of commercially exploited pelagic sharks. We used satellite telemetry as a fisheries-independent tool to document fisheries interactions, and quantify fishing mortality of the highly migratory shortfin mako shark ( Isurus oxyrinchus ) in the western North Atlantic Ocean. Forty satellite-tagged shortfin mako sharks tracked over 3 years entered the Exclusive Economic Zones of 19 countries and were harvested in fisheries of five countries, with 30% of tagged sharks harvested. Our tagging-derived estimates of instantaneous fishing mortality rates ( F = 0.19–0.56) were 10-fold higher than previous estimates from fisheries-dependent data (approx. 0.015–0.024), suggesting data used in stock assessments may considerably underestimate fishing mortality. Additionally, our estimates of F were greater than those associated with maximum sustainable yield, suggesting a state of overfishing. This information has direct application to evaluations of stock status and for effective management of populations, and thus satellite tagging studies have potential to provide more accurate estimates of fishing mortality and survival than traditional fisheries-dependent methodology.
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Cass, Philip. "REVIEW: Noted: ‘All we want is a fairer share’." Pacific Journalism Review : Te Koakoa 28, no. 1 & 2 (July 31, 2022): 264. http://dx.doi.org/10.24135/pjr.v28i1and2.1258.
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Our Ocean’s Promise: From aspiration to inspiration: The Marshall Islands Fishing story, by Giff Johnson. Majuro: Marshall Islands Marine Resources Authority, 2021, 200 pages.
THIS lavishly illustrated history of the development of commercial fishing in the Marshall Islands will be of interest to anybody concerned with economic development and sensible management of fishing stocks in the Pacific. For many islands their offshore economic zones and fishing fields have been a source, even potentially, of wealth. However, overfishing and the loss of fishing stock through legal agreements, leasing arrangements and outright piracy have been a problem for many island states in recent years.
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EZGETA -BALIĆ, DARIA, NEDO VRGOČ, IGOR ISAJLOVIĆ, DAMIR MEDVEŠEK, ANTE VUJEVIĆ, MARIJA DESPALATOVIĆ, and IVAN CVITKOVIĆ. "Comparison of beam trawl catch, by-catch and discard in fishing and non-fishing areas – a case study from the northern Adriatic Sea." Mediterranean Marine Science 22, no. 1 (February 12, 2021): 108. http://dx.doi.org/10.12681/mms.24973.
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Beam trawl fishery is highly important in the Croatian part of the northern Adriatic wherein 116 vessels have a licence for this type of fishing gear. A sharp decrease in the beam trawl catch observed since 2015 has raised concern about not only socio-economic issues but also ecological issues and the effect that beam trawl fisheries have had on exploited stocks. Besides the effect that beam trawl fisheries can have on targeted economically important species, intensive dredging can cause long-term changes in the benthic community. Therefore, this study aimed to detect the effect that this type of fishing gear has on target and by-catch species. Furthermore, survey data were compared with the official beam trawl fishery data gathered through Vessel Monitoring System data together with fishermen’s logbooks. Our research targeted two adjacent areas: an area where beam trawl fishing is allowed and an area where it is forbidden. The results demonstrate that the commercially important catch represented a minor share of the total beam trawl catch in both survey areas, while discard made up more than 93% of the total catch. The main beam trawl commercially important species in the Croatian part of the northern Adriatic Sea was Pecten jacobaeus, followed by Solea solea and Ostrea edulis. Our results suggest that beam trawl fisheries mostly affect target bivalve species and some non-commercial benthic species (e.g. sponges). The differences recorded between areas could suggest that beam trawl fisheries cause changes mostly in the P. jacobaeus population.
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Georgeson, L., C. L. Rigby, T. J. Emery, M. Fuller, J. Hartog, A. J. Williams, A. J. Hobday, et al. "Ecological risks of demersal fishing on deepwater chondrichthyan populations in the Southern Indian and South Pacific Oceans." ICES Journal of Marine Science 77, no. 5 (March 24, 2020): 1711–27. http://dx.doi.org/10.1093/icesjms/fsaa019.
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Abstract Risks to deepwater chondrichthyans (sharks, rays, and chimaeras) from fishing are poorly understood, particularly in areas beyond national jurisdiction. We adapted productivity–susceptibility analysis (PSA) and sustainability assessment for fishing effects (SAFE) to assess the vulnerability of 173 deepwater chondrichthyans to various demersal fishing gears in the Southern Indian and South Pacific Oceans. Several species were categorized as being at high or extreme vulnerability, including some deepwater shark species in the Southern Indian Ocean that are reported to be commercially targeted. There was good concurrence between PSA and SAFE results for species categorized as being at high or extreme vulnerability by the SAFE, but as expected there was an overall greater number assessed to be as higher vulnerability using PSA due to its precautionary nature. Our results indicate probable misclassifications in the PSA relative vulnerability rankings, highlighting the value of applying more quantitative tools, such as SAFE, when adequate data are available. Our findings indicate that better catch, effort, and biological information are needed to inform the assessment and management of deepwater chondrichthyans. If targeted fishing of deepwater shark species continues in the Southern Indian Ocean, improved assessments and estimates of sustainable yields are urgently required to mitigate the risk of overexploitation.
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Rudyk-Leuska, N. Ja, І. Yu Buzevych, M. V. Leusky, G. O. Kotovska, and D. S. Khrystenko. "СТРУКТУРНI ПОКАЗНИКИ ПОПУЛЯЦІЇ КАРАСЯ СРІБЛЯСТОГО (CARASSIUS GIBELIO B.) КРЕМЕНЧУЦЬКОГО ВОДОСХОВИЩА." Scientific Issue Ternopil Volodymyr Hnatiuk National Pedagogical University. Series: Biology 82, no. 3 (November 23, 2022): 44–51. http://dx.doi.org/10.25128/2078-2357.22.3.7.
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Ukraine ranks first in Europe in the number of natural water bodies. These abundant water resources are the source of significant fish resources, which are effectively exploited by the fishing industry. Rationalization and equal distribution of the commercial load, the reduction of the commercial pressure on the main fish species has always been an urgent issue. This can be achieved by shifting the focus of fishing to other types of fish, which will allow rational use of the entire complex of commercial species. The Prussian carp Carassius gibelio (Bloch, 1782) is among such promising objects of fishing - a massive, small-particle species, which in certain water bodies of Ukraine has displaced other minor commercial fish species and formed stable numerical populations.
A decisive role in the age structure formation of the Prussian carp population was played by the increase in the specific number of middle and older age groups, which is associated with an insufficient level of commercial load. Thus, the variation series of this species in the commercial catches of 2021, unlike other species, had the form of a double-peaked curve, which was formed due to the loss of size classes of 25-28 cm. According to the Fishing Rules and the Regime of Fishery Operation of the Dnipro Reservoirs in force today, nets with a step are allowed hole a=38-49 mm and 70 mm and more. This distribution of commercial load selectivity reduces pressure on bream and bream populations. However, it also causes a significant increase in the stock of Prussian carp. And this alien species has formed abundant populations in the Kremenchuk Reservoir. Thus, its average annual catch in the period 2000-2020 increased from 44.6 to 462.4 tons or 10 times in 20 years.
We should note that Prussian carp occupied an insignificant segment of the catch - no more than 0.1% by weight in the traditional commercial set of gill nets (a=75-90 mm) at the Kremenchuk Reservoir, while, in the 50-60 mm mesh size nets this species is dominant with a share in catches of up to 60% by weight. Thus, the main indicators that characterize the fisheries and environmental protection components of gill net fishing are a mesh size that deals with part of the main target fishing objects, size and weight indices, and bycatch of immature commercially valuable species. The gill nets with 50-60 mm generally meet the requirements for the current legislation and might be used for targeted harvest of the species in the littoral zones. Considering the need to intensify fishing for Prussian carp and its high actual specific mass in catches of nets with a mesh size of 50-60 mm, the implementation of specialized fishing for this species in the Dnieper reservoirs can be considered as a means of optimizing the use of the formed bioresource for the commercial fishery. In order to minimize the negative impact of this fishing on the structural and functional indicators of the bream population, specialized fishing should be focused on the areas of accumulation of Prussian carp, i.e. it is a specialized fishery with a share of Prussian at least 50%. The necessity of the meliorative capture introduction aimed to downgrade the reproductive core of the population of this alien species to prevent its uncontrolled population growth.
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Novianto, Dian, and Budi Nugraha. "KOMPOSISI HASIL TANGKAPAN SAMPINGAN DAN IKAN TARGET PERIKANAN RAWAI TUNA BAGIAN TIMUR SAMUDERA HINDIA (Catch Composition of By-Catch and Target Species on Tuna Longline Fisheries in Eastern Indian Ocean)." Marine Fisheries : Journal of Marine Fisheries Technology and Management 5, no. 2 (September 28, 2016): 119. http://dx.doi.org/10.29244/jmf.5.2.119-127.
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<p>ABSTRACT<br />Tuna longline operations also capture other than tuna species are known as by-catch are caught accidentally due to the ecological linkages. This study aims to identify the species composition of by-catch and try to analyzed the interaction of non-target species with tuna species as the target species on tuna longline fishery in the eastern Indian Ocean. Surveillance was conducted on February 2013-January 2014 by following 7 commercial tuna longliners vessel with fishing operations for 226 days. The results showed there were 36 species, where the target species consists of 4 tuna species (26.11%) and 32 by-catch species consist of by-product (24.08%) and that is not utilized (discards, 49.74%). The Results of by-catch are consists of a lancetfish (Alepisaurus spp., 42.87%), pelagic stingray (Pteroplatytrygon violacea, 22.05%), escolar (Lepidocybium flavobrunneum, 10.22%) and sickle pomfret (Taractichthys steindachneri, 8.21%), while for other species consists of are billfishes (6 species), shark and rays species (10 species), bony fishes (11 species) and turtles (olive ridley).</p><p>Keywords: by-catch, tuna longline, Indian ocean</p><p>-------</p><p>ABSTRAK</p><p>Pengoperasian rawai tuna juga menangkap jenis-jenis lain selain tuna yang dikenal dengan sebutan hasil tangkap sampingan (HTS atau by-catch) yang tertangkap secara tidak sengaja dikarenakan adanya keterkaitan secara ekologi. Penelitian ini bertujuan untuk mengidentifikasi komposisi jenis hasil tangkap sampingan dan mencoba menganalisis hubungan interaksi ikan hasil tangkap sampingan dengan ikan tuna sebagai tangkapan utama (target species) pada perikanan rawai tuna di bagian timur Samudera Hindia. Pengamatan dilakukan pada bulan Februari 2013-Januari 2014 dengan mengikuti kegiatan operasi penangkapan 7 kapal rawai tuna komersial dengan selama 226 hari operasi penangkapan. Hasil penelitian menunjukkanterdapat 35 jenis ikan dan 1 jenis penyu dimana target utama terdiri dari 4 jenis ikan (26,11%) dan hasil tangkapan sampingan 31 jenis ikan dan 1 jenis penyu dimana yang dimanfaatkan (by-product) (24,08%) dan yang tidak dimanfaatkan (discards) (49,74%). Hasil tangkapan sampingan berturut-turut didominasi oleh ikan naga (Alepisaurus spp., 42,87%), pari lemer (Pteroplatytrygon violacea, 22,05%), ikan setan (Lepidocybium flavobrunneum, 10,22%) dan bawal sabit (Taractichthys steindachneri, 8,21%), selanjutnya juga tertangkap jenis paruh panjang (billfish, 6 spesies), jenis cucut dan pari (elasmobranchii, 10 spesies), jenis teleostei (bony fishes,11 spesies) dan penyu lekang (Lepidochelys olivacea).</p><p><br />Kata kunci: Hasil tangkap sampingan, rawai tuna, Samudera Hindia</p>
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Xu, Xucai, and Russell B. Millar. "Estimation of Trap Selectivity for Male Snow Crab (Chionoecetes opilio) Using the SELECT Modeling Approach with Unequal Sampling Effort." Canadian Journal of Fisheries and Aquatic Sciences 50, no. 11 (November 1, 1993): 2485–90. http://dx.doi.org/10.1139/f93-273.
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An experiment was conducted to study trap selectivity for male snow crab (Chionoecetes opilio) in St. Mary's Bay, Newfoundland. The finishing effort of large-mesh commercial traps and small-mesh control traps was not equal because two commercial traps were fished for every control trap. We show how the SELECT (Share Each Length's Catch Total) method extends to this situation and, more generally, to selectivity trials in which catches are sampled in unequal proportion. Application to the crab data showed that a good fit was provided by the logistic selection curve under the assumption of unequal fishing efficiencies of commercial and control traps. The carapace widths at the retention probabilities of 0.25, 0.50, and 0.75 were estimated to be 86.4, 94.6, and 102.9 mm, respectively, and the retention probability at the minimum legal size of 95 mm was estimated to be 0.51. The commercial traps had almost twice the fishing efficiency of the control traps and consequently caught more legal-sized crabs per trap.
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Ben-Hasan, A., C. Walters, V. Christensen, G. Munro, U. R. Sumaila, and A. Al-Baz. "Age-structured bioeconomic model for strategic interaction: an application to pomfret stock in the Arabian/Persian Gulf." ICES Journal of Marine Science 77, no. 5 (April 25, 2020): 1787–95. http://dx.doi.org/10.1093/icesjms/fsaa049.
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Abstract When fish stocks migrate across multiple exclusive economic zones (EEZs), they compel managers to examine management at both national and international levels. A strategic interaction emerges when the fishing activity of one country impacts fishing opportunities available for other countries sharing the stock. Left unaddressed, strategic interaction could lead to overexploitation and suboptimal payoffs. Here, we develop and apply a bioeconomic model to address the competitive fishing for silver pomfret in the Arabian/Persian Gulf—a highly commercial fish stock shared between Kuwait and Iran—and evaluate biological–economic trade-offs under competition, cooperation, and country-independent management using maximum sustainable yield (MSY) and fishing mortality that maintain MSY (Fmsy) policies. When cooperation involves an equal share of the overall Fmsy or a share based on the proportion of the stock available in each EEZ, countries are expected to cooperate given the substantially higher catch, biomass, and relative profits compared to other management regimes. However, other than these two arrangements, countries would favour different regimes. Besides providing policy insights to improve the perilous status of silver pomfret, our approach could be useful in exploring alternative fishing arrangements to sustainably harvest a transboundary fish stock while maximizing average yields.
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Stevens, J. D., G. J. West, and K. J. McLoughlin. "Movements, recapture patterns, and factors affecting the return rate of carcharhinid and other sharks tagged off northern Australia." Marine and Freshwater Research 51, no. 2 (2000): 127. http://dx.doi.org/10.1071/mf98158.
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Between February 1983 and May 1985, ~10 500 sharks of 23 species were fin-tagged off northern Australia. Tagging concentrated on the commercially important Carcharhinus tilstoni and C. sorrah. Most recaptures were made in 1984 and 1985, but returns continued until May 1997. In all, 579 tags (5.5%) were recovered. Tag shedding was estimated to be low (0.025 year –1 for C. tilstoni) and tagging mortality was significantly lower for sharks caught by hand-line than by gill-net. Australian gill-netters, Taiwanese gill-netters (fishing in the Australian Fishing Zone) and Australian prawn trawlers accounted for most of the returns. The maximum distance between the release and recapture positions was >1100 km, but most returns were made within 50 km of the tagging site. Nearly all the releases were in inshore waters fished by Australian vessels. Although many recaptures were made by the offshore Taiwanese fishery, the Taiwanese fishing effort was much higher than for the inshore Australian fishery, so that relative to fishing effort, relatively few sharks moved from inshore to offshore waters.
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Savina, Marie, Robyn E. Forrest, Elizabeth A. Fulton, and Scott A. Condie. "Ecological effects of trawling fisheries on the eastern Australian continental shelf: a modelling study." Marine and Freshwater Research 64, no. 11 (2013): 1068. http://dx.doi.org/10.1071/mf12361.
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The New South Wales Offshore Trawl Fishery began to expand in 1976, following a large exploratory trawl survey carried out on the fishing grounds of the upper continental slope. This survey was repeated 20 years later with the same vessel and using similar protocols. Comparison of the survey results suggested that the overall fish biomass in the survey area had substantially decreased after 20 years. We have implemented an ecosystem model using the Atlantis framework to (1) emulate the evolution of the shelf ecosystems from 1976 to 1996 and (2) explore the effects of alternative fishing pressures on those ecosystems. We have been able to emulate the observed decline of most of the commercial groups of fish species in the Offshore Trawl Fishery, including sharks, and our results confirmed that fishing pressure was the most important cause of these observed changes. Fourteen fishing scenarios highlight the competing nature of some of the ecosystem-based sustainable fishing objectives.